Jan. 23, 2012 -- Two legally blind women with macular degeneration are the first people ever to get new retina cells grown from human embryonic stem cells.

One patient has dry macular degeneration, the top cause of blindness in developed nations. The other has Stargardt's disease, the leading cause of macular degeneration in young people. Both diseases are untreatable. Both get progressively worse.

But instead of progressively losing more retinal cells, new cells are growing in the treated eyes. And while both women still have permanent central vision loss, both seem to see a little better.

"They do have some improvement in peripheral vision around the central blind spot, which is not coming back," study co-leader Steven D. Schwartz, MD, chief of the retina division at Los Angeles' Jules Stein Eye Institute, tells WebMD.

Schwartz warns that the stem cell treatment is being developed as a way to prevent blindness in people with early-stage macular degeneration. It's not a treatment for blindness, he says.

But to test the safety of this first-ever-in-humans treatment, the study enrolled patients with very advanced disease -- and very little vision to lose in case anything went wrong.

But the two patients did not get worse, says study co-leader Robert Lanza, MD. Lanza, a pioneer of stem cell research, is chief scientific officer for Advanced Cell Technology Inc., the company that is developing the treatment.

"Before treatment, one patient could only see hand motion. She could not read any letters [on an eye chart]," Lanza tells WebMD. "By one month she could read five letters. But that does not capture the difference in her life. She could see more color. She had better contrast in the operated eye and no improvement in untreated eye. She mentioned she could start using her computer and even start reading her watch."

Lanza and Schwartz warn that this improvement could simply be a placebo effect. They're only the first two of 24 patients in the study. And it's only a phase I study designed to test safety, not effectiveness.

"The real value of this report is what we're learning about stem cell biology, about the safety of the treatment, about the lack of immune rejection, and about how these new cells engraft in the eye," Schwartz says.

And that's a big deal, says Anthony Atala, MD, director of the Institute for Regenerative Medicine at Wake Forest University.

"This is an exciting first step, albeit preliminary," Atala tells WebMD. "This is the first published report of patients treated with human embryonic stem cells with a follow-up that shows both safety and efficacy."

In the study, the women received new RPE cells grown from human embryonic stem cells. Embryonic stem cells have been tested in humans only once before -- in paralyzed patients with injured spinal cords. Results of those studies, now canceled, were never officially reported.

That makes the Schwartz/Lanza study the first official report of a treatment using human embryonic stem cells.

Advanced Cell Technology has developed a technique for obtaining embryonic stem cells without harming the embryo. But the current study, begun before this technique was invented, uses cells from an extra embryo created and discarded during an in vitro fertilization procedure.

Because the new retinal cells came from an unrelated embryo, there's the chance that patients' immune systems will reject the cells. There's very little of this kind of immune response within the eye, but patients in the study still undergo treatment with immunity-suppressing drugs.

Lanza says the two treated patients continue to do well six months after treatment. These women received 50,000 stem-cell-derived RPE cells. Dosages will be increased in subsequent patients up to 200,000 cells.

For comparison purposes, each patient is treated in one eye only.

A 24-patient European phase I trial, similar to the U.S. study, last week began enrolling patients.

If the treatment continues to prove safe -- still a big question mark -- larger studies will be planned. Even if everything goes perfectly, it will be years before a large-scale clinical trial begins accepting patients.

At least two patients may not have to wait that long. Lanza says the first two patients have each asked to be treated in the other eye.

"Much remains to be seen -- literally," Atala writes in an editorial accompanying the Schwartz/Lanza report in the Jan. 23 online issue of The Lancet.